The most common example of a flat concrete product, which is supposed to be manufactured in the machine in accordance with the invention, is a roof tile, whose top side as a rule shows linear generatrixes in its length direction, while its cross-section shows a wave-formed profile. Most frequently the roof tiles occurs as single- or double-cupped roof tiles, but a great number of variants will occur. The under side of the roof tile always is provided with knobs for mounting of the roof tile. The thickness of the roof tile can vary depending on its strength resistance, density and e.g. eventual suspension means. The manufacturing of concrete roof tiles are almost exclusively made by so called extrudation. This means that the concrete mass is compacted in a device including a rotary roller followed by a so called compacting block, which contacts the concrete, which is applied to the top side of the moulding trays in the machine. The demand for compacting of the concrete mass is considerable. In most countries standard demands of around 150-250 kg linear load on each cured roof tile occur together with a demand of a complete watertightness. The average thickness of the roof tile varies from 10 mm to around the dubble thickness at the knobs for the mounting of roof tile. This results in a considerable compacting force on the moulding tray when passing below the compacting unit.
An example of a machine in accordance with the preamble above is described in the Swedish patent publication SE 427 815. The machine in accordance with this patent publication is based upon two parallel chains which continuously pull the bed plates through the machine below a compacting unit, which consists of a rotating roller, and which is followed by a compacting block. The chains are standard roller chains, which have been provided with special links by which the bed plates are mounted to the chains. A special link and a number of standard links thereby show the same length as a roof tile. Each moulding tray is carried by two bed plates, at which the front bed plate is linked connected to the chains and at which the two other bed plates are linked connected to the first bed plate to make it for the bed plates to follow the chain around the chain wheel which are arranged at the two ends of the machine.
The Swedish patent publication SE 337 339 shows a similar machine for continuous manufacturing of roof tiles. The bed plates are, in accordance with this patent publication, not moved ahead by chains or the similar, but the plates are interconnected to one chain, at which threebed plates together will be used to support one moulding tray. Similar machines are known from the Swedish patent publications SE 160 527, SE 148 389 and SE 144 538.
A drawback with the known machines is that the bed plates in these can not be made with a length such that a moulding tray can be supported by one bed plate. The reason is that a too long bed plate can not be moved over a chain wheel, without projecting in the row of moulding trays passing through the machine, if this chain wheel will not have a relatively large diameter. This makes the machine space demanding and heavy. Another drawback consists in that several linked bed plate segments have links which will be torn out, and reducing precision in placing the moulding trays on the bed plates.